The present invention relates to a device used in conjunction with a reference plane device to accurately mount a cast of a patient's teeth on a dental articulator.
The purpose of a dental articulator is to stimulate the jaw or condylar movements of a patient. This instrument enables a dentist to obtain the necessary diagnostic information for the treatment of occlusal irregularities, such as malocclusion, and the fabrication of dental casts or dentures.
In a human, the lower jaw or mandible moves both laterally and vertically with respect to the upper jaw or maxilla. The mandible is hinged to the maxilla by means of two temporomandibular joints which are found on the sides of the head of a person near the ears. This joint consists of a condyle, which is part of the mandible, and which moves in a ball-and-socket-type joint and is joined to the maxilla by human cartilage and other tissue. A line running between a person's temporomandibular joints would define an imaginary "hinge axis" about which the mandible would rotate with respect to the maxilla.
A dental articulator consists of a lower frame and upper frame which move relative to each other so as to simulate the movement of the human mandible relative to the maxilla. In the case of the articulator, however, the upper frame or maxilla is moved relative to the lower frame or mandible, while in a human, the reverse is true. Nonetheless, it has been found that this fact makes no difference with respect to occlusal analysis. The hinging action of the articulator is accomplished by means of a pair of guide blocks which are mounted in the upper frame and which have openings on their lower surfaces to receive a pair of styluses correspondingly mounted on the lower frame. The styluses generally represent the human condyles and provide a hinge axis about which the upper frame can rotate and move. The hinge axis in the articulator, which corresponds to a patient's hinge axis, is a line through the centers of the styluses.
In U.S. Pat. No. 3,452,493, issued to Robert L. Lee on July 1, 1969, there is described a system of jaw movement simulation wherein the dynamic movement of the patient's jaws is reported and from this information, plastic guide blocks are formed. In U.S. Pat. Nos. 4,034,474 and 4,034,475, both issued to Robert L. Lee on July 12, 1977, there is suggested that plastic guide blocks of the type disclosed in the earlier Lee patent be classified according to certain characteristics of jaw movements to provide a series of average value blocks from which the pair most closely fitting the measurements of a particular patient's condylar movements may be selected. Further examples of such a system are disclosed in U.S. patent application, Ser. No. 814,815 which is pending. These blocks have three dimensional openings or pathways cut therein which receive a stylus, thus enabling a dentist to treat accurately an occlusal or denture problem without requiring the presence of the patient.
In order to efficiently utilize the articulator in simulating the jaw movements of a particular patient, it is not enough to simply select the proper pair of guide blocks. It is also just as important that the dental casts of the patient's maxillary and mandibular teeth be accurately mounted in the articulator so that their relative position is the same as they would be in the patient's mouth. The mounting device of the present invention is utilized in conjunction with the articulator and a face bow which establishes the location of the patient's hinge axis with respect to a reference plane, and is used for accurately mounting the dental casts on the articulator.
It is convenient to support the upper frame of an articulator on the lower frame while mounting a dental cast to the upper frame. However, the styluses on the lower frame forming a hinge axis tend to interfere with the operation unless they are conveniently laterally adjustable. In some prior art arrangements the styluses must be removed and cumbersome auxiliary equipment is required for transferring face bow reference plane information to the articulator.
In the system of the above-referenced Lee patents, it has been found desirable to have the styluses on the articulator spaced a fixed distance. Greater accuracy and consistency can be attained with fixed styluses and it has been found unnecessary that the styluses be spaced a distance equal to the spacing of the patient's condyles. However, the face bow used in locating the patient's condylar hinge axis must be adjustable in width to engage th patient's head against the tempromandibular joints. Thus, it is desirable that means be provided for easily transferring the face bow information to a fixed stylus articulator and other articulators in which it is not convenient to laterally adjust the styluses.